1. Field of the Invention
The present invention relates to a high vacuum apparatus, and more particularly to a high vacuum apparatus for fabricating a semiconductor device that is capable of preventing contaminant particles from generating due to cooling and condensing of reactive gas. The present invention also relates to a method for growing an epitaxial layer with less contaminant particles.
2. Description of the Background Art
As semiconductor devices get to have a higher function and become more highly integrated, contaminant degree due to contaminant particles directly affects the yield of a product.
Thus, efforts are increasingly made with importance to analyze the cause of generation of the contaminant particles and reduce the contaminant particles. Such efforts are important for the clean room environment and a gas convey system of semiconductor process equipment, and more importantly, it is more critical for equipment for performing processes since more contaminant particles are generated especially therein.
In an effort to solve the problems, according to an experiment on the cause of contaminant particles within a high vacuum reactive chamber for forming an epitaxial thin film by the present inventors, they noted that the position relationship between a gas inlet and a gas outlet has much influence on the generation of contaminant particles.
FIGS. 1A through 1C are sectional views of a high vacuum reactive chamber in accordance with a conventional art.
FIG. 1A is a sectional view of a high vacuum reactive chamber in accordance with a first embodiment of a conventional art.
With reference to FIG. 1, there is shown a reactive chamber 100. A gas inlet 106 is installed at one wall side of the reactive chamber 100, and a gas outlet is formed at the bottom of the reactive chamber 100. The gas outlet is connected with a vacuum pump.
A suscepter 102 is installed in the reactive chamber 100, on which a semiconductor substrate 104 is mounted.
In the apparatus of FIG. 1, when an epitaxial thin film is deposited at the upper surface of the semiconductor substrate 104, the reactive gas supplied into the reactive chamber 100 through the gas inlet 106 forms a gas flowing 100a in the direction parallel to the upper surface of the substrate 104 at the upper portion of the substrate 104, and a discharge gas is discharged through the gas outlet provided at the lower center portion of the reactive chamber 100 to communicate with the vacuum pump (not shown).
FIG. 1B illustrates an inspection result according to observation of contaminant particles of the semiconductor substrate processed in the reactive chamber of FIG. 1A.
With reference to FIG. 1B, there are observed short band-shaped particles 105 in the same direction as the gas flowing 100a on the substrate 104.
FIG. 1C illustrates the result of measurement of the number of contaminant particles for the semiconductor substrate of FIG. 1B.
As shown in FIG. 1C, the number of contaminant particles is shown by regions. It is noted that the more distance from where the substrate 104 initially contacts the gas flowing 100a becomes, the more the contaminant particles. That is, the region 107a includes the most contaminant particles in number, the region 107b has the middle number of contaminant particles, and the region 107c has the least contaminant particles.
In other words, the region 107c nearest to the gas inlet has the lowest contamination level while the region 107a farthest to the gas inlet has the highest contamination level. The reason for this is judged that the reactive gas is dispersed from the gas inlet, collides with the inner wall of the opposite reactive chamber, cooled and condensed to generate the contaminant particles.
FIGS. 2A through 2C are diagrams for explaining generation of contaminant particles in the high vacuum reactive chamber in accordance with the second embodiment of the conventional art.
FIG. 2 is a sectional view of a high vacuum reactive chamber 200 in accordance with a second embodiment of the conventional art.
With reference to FIG. 2A, a reactive chamber 200 is shown. A gas inlet 206 is formed at the ceiling of the reactive chamber 200 and a gas outlet is installed at the bottom of the reactive chamber 200, to which a vacuum pump is connected.
A suscepter 202 is installed at the central portion in the chamber 200, on which a semiconductor substrate 204 is mounted.
When an epitaxial layer is deposited at the upper surface of the semiconductor substrate 204 by using the apparatus of FIG. 2A, the reactive gas is supplied through the gas inlet 206 installed at the center of the ceiling of the chamber 200 to the reactive chamber 200, forming the gas flowing 200a in the direction in which the gas collides with the center of the semiconductor substrate 204. A discharge gas is discharged through the gas outlet provided at the center of the bottom of the reactive chamber 200 to communicate with a vacuum pump (not shown).
FIG. 2B is a diagram showing a result of inspection with naked eye of the contaminant particles of the semiconductor substrate which has undergone the processes in the reactive chamber of FIG. 2A.
With reference to FIG. 2B, as the gas flowing 200a collides with the substrate 204, a collision form of pattern 205 was observed around the center of the substrate 204.
FIG. 2C is a diagram showing a result of measurement of the number of the contaminant particles of the semiconductor substrate of FIG. 2B. FIG. 2C also shows the number of contaminant particles by regions, of which, notably, the region 207a where the substrate 204 first collides with the gas flowing 200a includes many contaminant particles, whereas less contaminant particles were observed in the region 207b, which is distant from the region 207a. 
This result shows somewhat different from that of FIG. 1C where the farther the reactive gas becomes distance from the gas inlet, the more contaminant particles are generated. The reason for this is considered that the reactive gas is heat-exchanged with the substrate 204 at the portion where the gas flowing 200a directly collides with the substrate 204, cooled and condensed to generate the contaminant particles. Thus, the position where the gas flowing initially collides with inside the reactive chamber 200 is one of principal variants to generate the contaminant particles.
FIGS. 3A through 3C are diagrams showing generation of contaminant particles in the high vacuum reactive chamber in accordance with a third embodiment of the conventional art.
FIG. 3A is a sectional view of a high vacuum reactive chamber in accordance with the third embodiment of the conventional art.
With reference to FIG. 3A, there is shown a reactive chamber 300, in which a suscepter 302 is installed. A semiconductor substrate 304 is mounted at the upper surface of the suscepter 302.
A gas injector 305 is installed at one side spaced apart from the suscepter 302, through which a reactive gas is injected into the reactive chamber 300.
The supplied reactive gas first collides with the wall of the dome-shape ceiling of the reactive chamber 300 or makes a gas flow indicated by a reference numeral 300a due to gravity of itself.
Meanwhile, a discharge gas is discharged through a gas outlet provided at the lower center of the reactive chamber 300, communicating with a vacuum pump (not shown).
FIG. 3B is a result of inspection with a naked eye of the contaminant particles of the semiconductor substrate which has undergone the processes in the reactive chamber of FIG. 3A. It is noted that a circular pattern 305 is widely observed in the portion where the gas flowing 300a contacts the substrate 304.
FIG. 3C is a diagram of a result of measurement of the number of the contaminant particles of the semiconductor substrate of FIG. 3B. Like the result of FIG. 1C, the farther the substrate 304 first contacts the gas flowing 300a, the more contaminant particles the region 307a has. The reason for this is also considered that the gas flowing 300a does not directly collide with the substrate 304 and as the gas flowing 300a becomes distant, it is more easily cooled and condensed to serve as the contaminant particles.
Therefore, an object of the present invention is to provide a high vacuum apparatus for fabricating a semiconductor device that is capable of preventing contaminant particles from generating due to the cooling and condensing of a reactive gas.
Another object of the present invention is to provide a method for growing an epitaxial layer with less contaminant particles by using the high vacuum apparatus.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an improved high vacuum apparatus for fabricating a semiconductor device including a reactive chamber provided with an inlet and an outlet for a reactive gas, a suscepter installed in the reactive chamber for mounting the semiconductor thereon and a vacuum pump connected with the outlet to make the inside of the reactive chamber to put in a high vacuum state, wherein a gas injector of the reactive gas inlet is directed downward of the semiconductor device so that the initial gas flowing of the reactive gas injected from the reactive gas inlet does not directly pass the upper portion of the semiconductor substrate mounted on the suscepter.
In the high vacuum apparatus for fabricating a semiconductor device of the present invention, the gas outlet is preferably formed at the side wall of the lower portion of the reactive chamber, and more preferably, a gas flow inducing unit for inducing the gas flowing of the reactive gas to the lower portion of the semiconductor substrate is provided at the gas injector.
In the high vacuum apparatus for fabricating a semiconductor device of the present invention, an induction pin inserted in the gas injector may be selected as the gas flow inducing unit. In this case, the induction pin is a hollowed cylinder type with its end portion closed and having a gas injector at the middle portion thereof, and the induction pin is preferably inserted into the gas injector so that gas injector is directed downward of the reactive chamber.
To achieve the above objects, there is also provided a method for forming an epitaxial layer by using the high vacuum apparatus for fabricating a semiconductor device, including the steps of: mounting a semiconductor substrate on the suscepter; operating the vacuum pump so that the pressure within the reactive chamber is in the range of 10xe2x88x929xcx9c10xe2x88x927 Torr; maintaining the temperature of the reactive chamber wall at 0xcx9cxe2x88x9220xc2x0 C.; heating the suscepter so that the temperature of the suscepter is maintained at 650xcx9c750xc2x0 C.; and injecting a reactive gas through the gas injector to form an epitaxial layer.
In the method for forming an epitaxial layer of the present invention, if the epitaxial layer is a silicon film, SiH4 or Si2H6 may be used as a silicon source gas.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.